Alternating-current welding system



o. H. EscHHoLz AND H. FA'HNOE. ALTERNATING CURRENT WELDING-SYSTEM. APPPICATION F|LED.0CT. 6. 1919.

TTORNEY UNITED STAMENT OFFICE:

omo H'. kEscruonz,l 'or WILKINsBUnG, AND HANS FAHNoE, or PITTSBURGH, PENN- SYLVANIA, ASSIG-NORS T WESTIN'GHOUSE ELECTRIC'ANI) PANY, A CORPORATION 0F PENNSYLVANIA.

MANUIACTUQR'ING COM;-

ALTEBNATING-CURRENT WELDING SYSTEM.

To all whom z't may concern.'

Be it known that we, Orro H. EsCHHoLz, a citizen of the United States, and a resident ofWilkinsbur ,in the county of Allegheny and State of ennsylvania, and HANS FAH- NoE, a citizen of the United States, anda resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Alternating- Current Weldintg. Systems, of which the following is a spec' cation.

Our invention relates to electric arc lwelding systems and, more particularly, to welding systems employing alternating current, and it has, forgits primary object, the provision of. welding systems which shall possess good startingcharacteristics and afford positive protection for the operator against shock hazards.

It has been found feasible to weld by means. of alternating current, but diiliculty has been experienced in establishing an arc,

which difficulty is believed toy be occasioned by the reversalsl of current. We have found that, by employing a relatively high voltage during the period of establishing an arc, and under welding conditions, the welding operation is greatly facilitated.` However, the

employment of a relatively high voltage introduces a definite shock hazard which is, ofV

course, undesirable. l

One obj ect of our invention resides, therefore, in the provision of means for automatically establishing a low open-,circuit voltage in alternating-current welding systems.

With these and other objects in view, our invention will be more fully described and illustrated in the drawing lwhich is a 4diagram of a Welding system embodying our invention.

- In practising our invention,we mayprovide a welding system ,by employing a transformer having primary and secondary wind-- ings, the secondary windingA of which may be connected to a plurality of electrodes. The primary winding is, of course, connected to a suitable supply circuit and w'prefer to employI an impedance, vsuch as a reactance, connected in series with the primary wind- We also employ mean's for lshunting Specication of Letters Patent. wlat'ented June 15, 1920. Application illed October 6, 1919. Serial No. 328,798.

In the drawings is shown a transformer lhaving a secondary coil 2 which is directlyreactance 5 is connected in series lwith the lurality of contact primary winding. A members 6 are connecte in parallel relation to the reactance 5 and are adapted to be brid ed by a bridging member of a switch 7. 'lhe switch 7 is provided witha lurality of switch-actuating coils Sand 9, t e coil -8 being connected in parallel relationto the primary winding 4' and the coil 9 being con"- nected in parallel relation to the secondary winding 2 and the electrodes 3.

In operating the above described welding system, the primary winding 4 is connected to a suitable alternating-current supply circuit having a sulliciently high voltage to facilitate establishing an arc between the electrodes 3. It has been found that a voltage of between 110 and 135 volts gives satisfactory results in facilitating the establishing of an arc by means of alternating current. A voltage of this value, however, introduces a shock hazard when welding is not being performed because the voltage available between the electrodes is sufficiently high if no means is provided to reduce the voltage.

The reactance 5, connected in series with the rimary winding 4, eifects a reduction of t e voltage available between the electrodes 3 when it is in circuit with the primary winding 4. The reactance 5 is, therel circuit, by the switch 7 bridging the contact members 6 under the influence of the coil 8, when an arc is establishedbetween the electrodes 3.

The coils 8 and 9 :are so wound as to be in opposition to eachother at all times and,

when welding is not being performed, the

full voltage, across thesecondary winding 2,

is impressed upon the coil 9 which opposesthe coil 8 to such an extent that the switch 7 remains in an open position. "It will be apparent, therefore, that under open-circuit conditions, the reactance 5 is always in series with the primary winding4, lthereby reducing the voltage available between the electrodes 3, which voltage may be made as low7 asdesired to protect the operator.

When it is desired to start welding, the electrodes 3 are engaged and then slowly separated in the usual manner, the voltage impressed upon the coil v9 being materially reduced while the voltage impressed upon the coil 8 remains substantially the same, andits action, therefore, overcomes the action of the coil 9 and causes the switch 7 to bridge the contact members 6. The reactance is thus shunted from the primary circuit when the electrodes are engaged, thereby making full voltage vavailable between the electrodes and facilitating the es,- tablishing of an arc.

It will be a preciated from the foregoing description o the welding system that we have provided sim le and inexpensive apparatus'i'which aiforcis positive protection to the operator. Furthermore, since the action of the protectivemeans is entirely automatic, the attention of the operator is not diverted from the work in order to insure that the apparatus ,shall perform its function.

Furthermore,l kby employing coils connected in arallel relatlon to the primary andp secon ary circuits, they need. not be designed to carry a heavy current and,

therefore, may be made light in weight andsensitive to changes in 'circuit conditions.

Although we have shown and specifically described a welding system which embodies our invention, it is obvious that minor changes may be made in the arrangement of the elements embodied in the system, and we desire, therefore, that no limitations shall be imposed except such as are indicated in the appended claims. We claim as our invention 1. An arc welding system comprising a `-\transfonner having primary and secondary windings, a lurality of electrodes connected to the secon ary winding, an impedance connected to the primary winding `and means for shunting the impedance from the rimary circuit, said means including a switch and a plurality of switch-actuating coils.

2. An arc welding system comprising a transformer having primary and secondary v windings, a plurality .of electrodes connected to the secondary wmding, an impedance connected to the primary winding and means for shunting the impedance from the primary` circuit, said means including a switch and a plurality of opposing switchactuating coils.

3. An arc welding system comprising a transformer having primary and secondary windings, a plurality of electrodes connected to the secondary winding, an impedance connected to the primary winding and means for shunting the impedance from the primary circuit, said means including a switch and a plurality of switch-actuating coils, one of which is connected in parallel relation to the secondary winding and another of which is connected in parallel relation to the primary winding.

4. An arc welding system comprising a transformer having primary and secondary nected in series with the primary winding,

a switch adapted to bridge a plurality of contact members connected in parallel relationto the impedance, and a plurality of opposing switch-actuatin coils adapted to actuate the switch to bri ge they contact members when an arc is drawn between the electrodes.

6. An arc welding system comprising a transformer having primary and secondary windings., a lurality of electrodes connected to the secon ary winding, an impedance connected in series with the prima winding, aswitch adapted to bridge a p urality of contact members connected in parallel relation to -the impedance, and two opposing switch-actuating coils, one of which 1s connected in parallel relation to the secondary lwinding and the other of which is .connected in parallel relation to the primary winding.

In testimony whereof, We have hereunto subscribed our names this 30th day of Sept.,

' OTTO H. ES-CHHOLZ.

HANS- FAHNOE. 

